The proposed research is central to addressing the educational needs of an at-risk population, families of Mexican-descent, who traditionally are underrepresented in high paying scientific and technological fields. The general objective of this research is to consider developmental and sociocultural influences on the development of scientific understanding in order to create innovative and socioculturally sensitive science curricula. Three studies examine four factors that influence parent-child explanatory conversations about floatation. These four factors are: Child age (3, 4, or 5 years-old), culture (European-descent or Mexican-descent), parent's education level (high school diploma & less than high school), and research setting (experimental or naturalistic). The specific aims of this research are: (1) Examine (child) age related differences in parent-child explanatory conversations about floatation. Hypothesis 1: Five year-olds and their parents engage in more extensive and elaborate explanatory conversations than four year-olds and their parents; (2) Examine cultural differences in parent-child talk about floatation. Hypothesis 2: In naturalistic settings there are no cultural difference in the quantity and quality of explanatory conversation. Hypothesis 3: In experimental settings, however, fewer explanations are offered by parents and fewer questions are asked by children of Mexican-descent than parents and children of European-descent; (3) Examine the way in which parent's education level influences parent- child explanatory conversations. Hypothesis 5: In experimental settings parents of lower educational levels offer fewer and less elaborate explanations to their children. Hypothesis 4: In naturalistic settings, parents with lower levels of education provide fewer and less elaborate explanations than more educated parents.